1. Technical Field of the Invention
The present invention relates broadly to the field of biomedical transducers and more particularly, to a passive sensor monitoring the heart of a fetus.
2. Related Art and Problem to be Solved
Conventional fetal heart monitoring sensors are described in U.S. Pat. Nos. 4,471,200, 4,784,154, 5,209,237 and 5,524,631. Several known fetal heart sensors utilize a belt having one or more sensor stations thereon. Common shielding is used for all the sensor stations. However, in many instances, the common shielding crackles and moves thereby causing noise and interference of the detected fetal heart acoustic signal.
Some prior known heart monitoring sensors utilize a layer of RTV silicone to function as external pads that provide electrical isolation of the patient with respect to the belt sensor assembly. However, the RTV silicone layer is susceptible to chipping thereby reducing the electrical isolation between the belt sensor assembly and the patient.
Accordingly, it is an object of the present invention to provide a fetal heart monitoring sensor that substantially eliminates the problems associated with known fetal heart monitoring sensors.
Other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which, in one aspect, is directed to a fetal heart monitoring system comprising a backing plate which can have a generally concave front surface and a generally convex back surface, and at least one sensor element attached to the concave front surface for acquiring acoustic fetal heart signals produced by a fetus within a body. The sensor element can have a shape that conforms to the generally concave back surface of the backing plate. In one embodiment, the at least one sensor element comprises an inner sensor, and a plurality of outer sensors surrounding the inner sensor. In one embodiment, the fetal heart monitoring system further comprises a web belt, and a web belt guide movably attached to the web belt.
The web belt guide is attached to the convex back surface of the backing plate. In another aspect, the present invention is directed to a method for simultaneously making a plurality of acoustic signal sensor elements, comprising the steps of providing a plurality of flex cables wherein each flex cable has a plurality of conductors thereon, equidistantly positioning the flex cables along a working surface, configuring each flex cable such that all but a first one of the conductors are folded upward, disposing a first electrically conductive adhesive layer over a portion of the first one of the conductors of each flex cable, disposing a first strip of piezoelectric film over the first electrically conductive adhesive layer, configuring each flex cable such that a second one of the conductors is disposed over the first strip of piezoelectric film, disposing a second electrically conductive adhesive layer over a portion of the second one of the conductors of each flex cable, disposing a second strip of piezoelectric film over the second electrically conductive adhesive layer, configuring each flex cable such that a portion of a third one of the conductors of each flex cable is disposed over the second strip of piezoelectric film, disposing a third electrically conductive adhesive layer over said portion of the third one of the conductors, disposing a metallic strip over the third electrically conductive adhesive layer and substantially the entire second strip of piezoelectric film, curing the adhesive layers to form a laminate assembly, providing a template having indicia thereon that functions as a cutting guide, and cutting the laminate assembly according to the indicia to form a plurality of sensor elements.